Semiconductors that contain nitrogen (N) as the Group V element have proven to be useful for short-wavelength light emitting devices because of their wide band gap. Among these, extensive research has been conducted on gallium-nitride based semiconductors for use as light emitting diodes, such as AlGaInN, and such light emitting diodes (LED) have already been put to practical use.
Generally, GaN-based LED are grown on a sapphire substrate. The sapphire substrate is rigid and electrically nonconductive and has a low thermal conductivity. In a typical process for making a GaN-based LED, an undoped GaN layer and a lightly doped n-type GaN layer are sequentially grown on a sapphire substrate. A heavily doped n-type GaN layer, an active layer with a multi-quantum well structure, and a p-type GaN layer are also sequentially grown on the lightly doped n-type GaN layer. One or more p-electrodes may then be formed on the p-type GaN layer. The sapphire substrate is removed using a laser lift off (LLO) process, exposing the n-type layers for subsequent etching and removal such that the n-type electrode contacts the lightly doped n-type GaN layer.
However, the known methods of manufacturing vertical GaN-based LEDs have limitations in that the LLO process can be inadequate and inefficient for manufacturing reliable, efficient LED. Also, due to the similar etching selectively of the various GaN layers, it can be difficult to differentiate the interface between the different layers. Accordingly, there is a need for a vertical LED and method of making a vertical LED that solves the shortcomings of known methods.